Truck beds are normally covered with a rigid shell or topper to protect cargo within the bed. These shells are restricted in height by their shape and do not adjust for loads of varying height. Liftable covers for the open portion or bed of trucks or trailers have been disclosed in the past. By example, U.S. Pat. No. 3,155,423 discloses a liftable vehicle top for a pickup truck issued to Cripe in 1964. A trailer vehicle for hot line tools with a top lifting mechanism is disclosed in U.S. Pat. No. 2,531,140 issued to Linde. Other truck cover devices include a foldable top for a truck bed issued to Geier in U.S. Pat. No. 4,964,669 and a collapsible truck bed covering structure as disclosed in U.S. Pat. No. 4,768,824 issued to Andonian.
The liftable tops listed above are unduly complex in the support structure and are expensive to install, making them undesirable to the average truck owner. Liftable tops disclosed above have mechanisms which occupy and interfere with the interior of the truck or trailer bed and reduce the storage capability. These liftable tops do not rest in a low profile position atop the truck frame. In fact, most have hinges or mechanisms such that the upper surface of the top or cover is at least several inches above the truck bed frame making the cover bulky and aesthetically unpleasing. Many consumers spend substantial sums of money purchasing or customizing a truck and value the contours of the truck shape. These consumers do not want shells or high profile covers disrupting the lines of the "classic" truck shape. Occasions arise, however, where these consumers have a need to cover cargo and desire some type of cover. Thus, there is a need in the truck cover industry for a liftable top with a low profile in the lowered position.